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Biomedical subjects

P Springer

Publications and source records attributed to P Springer.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Virtual CT colonoscopy. Examination technique, limitations and perspectives].

Virtual CT-colonoscopy is a post-processing method which allows for reconstruction of inner bowel surface structures from helical CT datasets. The reconstructed images simulate the views which are known from fiberoptic endoscopy. Since colorectal cancer is the second main cause of death in USA and Europe today and since recent screening recommendations are often ignored by the public, a non-invasive or minimal-invasive procedure for colonic evaluation would offer some benefits. Virtual CT-colonoscopy generally involves three essential steps: patient preparation with cleansing of the bowel and administration of an air enema, helical CT-examination by using appropriate scan parameters, and interactive 3D rendering of the volume data-set. Although recent studies have demonstrated that polypoid lesions of about 5 mm size are well detectable and although virtual colonoscopy offers many advantages over fiberoptic endoscopy, some technical and clinical limitations must still be noted. Thus, the current inability of virtual colonoscopy to provide texture and color leads to problems in identifying flat lesions; the presence of retained or adherent fecal matter may result to false positive diagnosis and collapsed segments of bowel may cause problems as they cannot subsequently be evaluated during image reconstruction. Virtual endoscopy is still in its infancy and further technical and clinical developments are necessary. Virtual CT-colonoscopy may then prove to be equal or superior to colonoscopy in sensitivity and specificity for polyp detection and be able to reduce the number of unnecessary colonoscopic procedures.

Colonoscopes↗
PubMed1996

[The smart-scan procedure of spiral computed tomography. A new method for dose reduction].

PURPOSE: In this article a new method - the Smart-Scan-Technique - for dose reduction during spiral computed tomography is described. This technique allows a dynamical adaptation of the tube current according to the measured local density structure form and absorption values of the object of interest. Its clinical applicability for dose reduction is investigated. In addition, changes in image quality are evaluated. METHODS: Specially designed, water filled plexiglas-phantoms, an Alderson-Rando phantom, and 20 patients were used to simulate possible measures of patients within the thoracic and abdominal region. For those two regions the dose reduction, the modulation transfer function, and the pixel noise were measured. RESULTS: Depending on patient geometry dose reduction up to 20% could be achieved with the Smart-Scan-Technique. This technique also enabled a decrease of the modulation transfer function and an increase of the pixel noise by 8%. CONCLUSION: Relevant dose reductions can be achieved by applying the Smart-Scan-Technique in spiral computed tomography.

Absorption↗
PubMed1996

[Establishment of an emergency CT service by means of teleradiology].

UNLABELLED: The teleradiological connection between the University Hospital in Innsbruck, Tyrol, and the Regional Hospital in Zwettl, Lower Austria, is presented as an example of a routine online connection of two helical CT systems. PURPOSE: To establish a practicable and cost-efficient emergency CT service in a remote hospital during night time and on weekends. MATERIAL AND METHODS: Online connection of a GE HiSpeed Advantage-Spiral-CT and a GE Prospeed-Spiral-CT via two Sun SPARC 10 work stations and ISDN. RESULTS: The transmission of 121 CT data sets from 116 patients revealed a sufficiently fast average transmission time of 15 (6-53) minutes and average transmission costs of DM 9.00 per examination. The system was technically reliable, cost-efficient and practicable in clinical routine application. CONCLUSIONS: Teleradiology enables remote hospitals to provide an emergency CT service even if there is no radiological specialist available outside office hours. Thus time-consuming and cost-intensive patient transfers and delay of therapy can be reduced.

Austria↗
PubMed1996

[PC-assisted network for quality control in film development].

Measuring of the daily performance of the film processing system by sensitometry is an important part of quality assurance in radiologic imaging. Computer-assisted evaluation of the measurements may be useful, especially in large hospitals with numerous image processors to be tested. We present a PC-based quality assurance network which was implemented at the University Hospital in Innsbruck in 1994. Direct data transfer from the evaluation stations to the technical service center of the hospital facilitated problem solving and resulted in a significant decrease of loss of time due to technical failures. An expansion of the network to outside institutions is planned for the future.

Computer Communication Networks↗
PubMed1995

Molecular genetic and protein chemical characterization of the cytochrome ba3 from Thermus thermophilus HB8.

Thermus thermophilus HB8 cells grown under reduced dioxygen tensions contain a substantially increased amount of heme A, much of which appears to be due to the presence of the terminal oxidase, cytochrome ba3. We describe a purification procedure for this enzyme that yields approximately 100 mg of pure protein from 2 kg of wet mass of cells grown in < or = 50 microM O2. Examination of the protein by SDS-polyacrylamide gel electrophoresis followed by staining with Coomassie Blue reveals one strongly staining band at approximately 35 kDa and one very weakly staining band at approximately 18 kDa as reported earlier (Zimmermann, B.H., Nitsche, C.I., Fee, J. A., Rusnak, F., and Münck, E. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 5779-5783). By contrast, treatment of the gels with AgNO3 reveals that the larger polypeptide stains quite weakly while the smaller polypeptide stains very strongly. These results suggested the presence of two polypeptides in this protein. Using partial amino acid sequences from both proteins to obtain DNA sequence information, we isolated and sequenced a portion of the Thermus chromosome containing the genes encoding the larger protein, subunit I (cbaA), and the smaller protein, subunit II (cbaB). The two polypeptides were isolated using reversed phase liquid chromatography, and their mole percent amino acid compositions are consistent with the proposed translation of their respective genes. The two genes appear to be part of a larger operon, but we have not extended the sequencing to identify initiation and termination sequences. The deduced amino acid sequence of subunit I includes the six canonical histidine residues involved in binding the low spin heme B and the binuclear center Cu(B)/heme A. These and other conserved amino acids are placed along the polypeptide among alternating hydrophobic and hydrophilic segments in a pattern that shows clear homology to other members of the heme- and copper-requiring terminal oxidases. The deduced amino acid sequence of the subunit II contains the CuA binding motif, including two cysteines, two histidines, and a methionine, but, in contrast to most other subunits II, it has only one region of hydrophobic sequence near its N terminus. Alignment of these two polypeptides with other cytochrome c and quinol oxidases, combined with secondary structure analysis and previous spectral studies, clearly establish cytochrome ba3 as a bona fide member of the superfamily of heme- and copper-requiring oxidases. The alignments further indicate that cytochrome ba3 is phylogenetically distant from other cytochrome c and quinol oxidases, and they substantially decrease the number of conserved amino acid residues.

Amino Acid Sequence↗
PubMed1995

Patterns of gene action in plant development revealed by enhancer trap and gene trap transposable elements.

The crucifer Arabidopsis thaliana has been used widely as a model organism for the study of plant development. We describe here the development of an efficient insertional mutagenesis system in Arabidopsis that permits identification of genes by their patterns of expression during development. Transposable elements of the Ac/Ds system carrying the GUS reporter gene have been designed to act as enhancer traps or gene traps. A novel selection scheme maximizes recovery of unlinked transposition events. In this study 491 plants carrying independent transposon insertions were generated and screened for expression patterns. One-half of the enhancer trap insertions and one-quarter of the gene trap insertions displayed GUS expression in seedlings or flowers, including expression patterns specific to organs, tissues, cell types, or developmental stages. The patterns identify genes that act during organogenesis, pattern formation, or cell differentiation. Transposon insertion lines with specific GUS expression patterns provide valuable markers for studies of Arabidopsis development and identify new cell types or subtypes in plants. The diversity of gene expression patterns generated suggests that the identification and cloning of Arabidopsis genes expressed in any developmental process is feasible using this system.

Arabidopsis↗
PubMed1995

[Magnetic resonance tomography in spinal trauma].

PURPOSE: To assess the value of MR imaging in the acute and chronic stages of spinal trauma. METHODS: 126 MR examinations of 120 patients were evaluated retrospectively. In 15 cases of acute spinal cord injury, correlation of MR findings with the degree of neurological deficit and eventual recovery was undertaken. RESULTS: Cord anomalies in the acute stage were seen in 16 patients. Intramedullary haemorrhage (n = 6) and cord transection (n = 2) were associated with complete injuries and poor prognosis, whereas patients with cord oedema (n = 7) had incomplete injuries and recovered significant neurological function. In the chronic stage, MR findings included persistent cord compression in 8 patients, syringomyelia or post-traumatic cyst in 12, myelomalacia in 6, cord atrophy in 9, and cord transection in 7 patients. CONCLUSION: In acute spinal trauma, MR proved useful in assessing spinal cord compression and instability. In addition, direct visualisation and characterisation of post-traumatic changes within the spinal cord may offer new possibilities in establishing the prognosis for neurological recovery. In the later stages, potentially remediable causes of persistent or progressive symptoms, such as chronic spinal cord compression or syringomyelia can be distinguished from other sequelae of spinal trauma, such as myelomalacia, cord transection or atrophy.

Acute Disease↗
PubMed1995

Analyzing job demands and coping techniques.

Surviving the stressful days nurses encounter in today's health-care environment involves sophisticated coping skills. This qualitative study found nurses responded with the use of "I" or "they" approaches to stressful situations. Nursing leaders are offered strategies for identifying and relating to these two groups of staff.

Adaptation, Psychological↗
PubMed1993

Cytochrome oxidase genes from Thermus thermophilus. Nucleotide sequence of the fused gene and analysis of the deduced primary structures for subunits I and III of cytochrome caa3.

Cytochrome caa3, a cytochrome c oxidase from Thermus thermophilus, has been purified and extensively characterized as a two-subunit enzyme containing the metal centers characteristic of cytochrome c oxidases (cytochromes a and a3; copper centers CuA and CuB) and an additional cytochrome c (Fee, J. A., Kuila, D., Mather, M. W., and Yoshida, T. (1986) Biochim. Biophys. Acta 853, 153-185). We have now cloned and sequenced the genes encoding the subunits of this enzyme. The smaller subunit consists of a typical oxidase subunit II sequence fused to a cytochrome c domain (Mather, M. W., Springer, P., and Fee, J. A. (1991) J. Biol. Chem. 266, 5025-5035). The larger subunit, the A-protein, is encoded by a fusion gene lying immediately downstream of the subunit IIc gene. The 5' portion of this gene encodes an oxidase subunit I homolog, whereas the 3' portion is homologous to oxidase subunits III. The A-protein from the purified enzyme appears too small from SDS-polyacrylamide gel electrophoresis and quantitative amino acid analyses to be a complete subunit I/III fusion, but it is currently not known if proteolytic processing occurs. Analyses of the sequences of oxidase subunits are presented which clearly identify T. thermophilus cytochrome caa3 as a bona fide member of the greater family of heme- and copper-requiring oxidases. As one consequence, it is confirmed that the set of invariant histidine residues (potential ligands of the metal centers) in cytochrome c oxidase subunits I and II is reduced to 8. Possible topological and helix packing models are developed based on considerations of homology, hydropathy, and variability.

Amino Acid Sequence↗
PubMed1991

Cytochrome oxidase genes from Thermus thermophilus. Nucleotide sequence and analysis of the deduced primary structure of subunit IIc of cytochrome caa3.

Cytochrome caa3, a cytochrome c oxidase from Thermus thermophilus, is a two-subunit enzyme containing the four canonical metal centers of cytochrome c oxidases (cytochromes a and a3; copper centers CuA and CuB) and an additional cytochrome c. The smaller subunit contains heme C and was termed the C-protein. We have cloned the genes encoding the subunits of the oxidase and determined the nucleotide sequence of the C-protein gene. The gene and deduced primary amino acid sequences establish that both the gene and the protein are fusions with a typical subunit II sequence and a characteristic cytochrome c sequence; we now call this subunit IIc. The protein thus appears to represent a covalent joining of substrate (cytochrome c) to its enzyme (cytochrome c oxidase). In common with other subunits II, subunit IIc contains two hydrophobic segments of amino acids near the amino terminus that probably form transmembrane helices. Variability analysis of the Thermus and other subunit II sequences suggests that the two putative transmembrane helices in subunit II may be located on the surface of the hydrophobic portion of the intact cytochrome oxidase protein complex. Also in common with other subunits II is a relatively hydrophilic intermembrane domain containing a set of conserved amino acids (2 cysteines and 2 histidines) which have previously been proposed by others to serve as ligands to the CuA center. We compared the subunit IIc sequence with that of related proteins. N2O reductase of Pseudomonas stutzeri, a multi-copper protein that appears to contain a CuA site (Scott, R.A., Zumft, W.G., Coyle, C.L., and Dooley, D.M. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 4082-4086), contains a 59-residue sequence element that is homologous to the "CuA sequence motif" found in cytochrome oxidase subunits II, including all four putative copper ligands. By contrast, subunit II of the Escherichia coli quinol oxidase, cytochrome bo, also contains a region homologous to the CuA motif, but it lacks the proposed metal binding histidine and cysteine residues; this is consistent with the apparent absence of CuA from cytochrome bo.

Amino Acid Sequence↗
PubMed1975

Motor effects of cholinergic stimulation of the globus pallidus in rats.

Forty-seven rats were cannulated permanently in either the globus pallidus or neostriatum and subsequently injected with carbachol, scopolamine, or carbachol plus scopolamine. The injection of carbachol (1 mug) into the globus pallidus produced transient hyperkinetic phasic dyskinesias (84%) followed in some cases by ipsilateral circling (47%) associated with hypertonic contralateral hind limbs. This condition progressed in some rats to a cataleptic state (42%). The injection of scopolamine (50 mug) or scopolamine (50mug) plus carbachol (1 mug) into the pallidum produced ipsilateral circling associated with hypotonia of the contralateral hind limb in a few rats. No hyperkinetic dyskinesias nor catalepsy were produced by these injections. The injection of carbachol (1 mug) into the neostriatum produced hyperkinetic dyskinesias (86%) of long duration, minimal circling (both directions) (10%), and catalepsy (29%). These effects were blocked by the addition of 50 mug of scopolamine to the carbachol injection. Scopolamine (50-100 mug) alone produced no effects after injection into the caudate/putamen. Saline injections in the neostriatum or globus pallidus produced no motor disturbance.

Animals↗